A method in which idle time retrieval is not lumped together but divided multistageously so that a burden on a host person for retrieving idle time for subjects of participation is lightened. The method, which is performed in an image forming apparatus to form images using toner, includes: rendering image data; deciding an amount of data of an image to be formed on a sheet using rendered results; and deciding a sheet feeding time point of a next sheet using a decided amount of data of the image. The management system includes a management network coupled to the first and second network elements and a processor element coupled to the management network and communicating with the first and second network elements through the management network. Additionally, at a wavelength of 1310 nanometers, the optical fiber possesses a mode field diameter of between about 8. In the removal position the can rolls from the first receptacle into the second receptacle, at the same time a new can is prevented from being conveyed from the conveyor into the first receptacle. By incorporating fluorine into a magnetic powder and controlling the crystal orientation in crystal grains, a magnetic material securing magnetic characteristics such as coercive force and residual flux density can be fabricated.